Re: Brain size, IQ

Ralph L Holloway (
Thu, 5 Sep 1996 22:49:12 -0400

On 5 Sep 1996, Gerold Firl wrote:

> |> For whatever it is worth, here follows some recent compilation of these
> |> fossil hominid brain volumes: from Indonesia, HE 1, 953;HE2 ,815; HE 4,
> |> 900; HE 6, 855; HE7, 1059; HE 8, 1004; Sambun17, 1035. The mean = 945.8.
> |> The Chinese from Z11, 1030; Z3, 915; ZV, 1140; ZVI, 850; ZX, 1225; ZXI,
> |> 1015; ZXII, 1030; Hexian, 1025. Mean = 1028.75. Lantian 2 is 780, which I
> |> would place more toward the indonesian time frame. Indonesian Solos:
> |> SoloI, 1172;Solo V, 1250; SoloVI, 1013; Solo IX, 1135; Solo X, 1231; Solo,
> |> XI, 1090. Mean = 1148.5. So the progression is from Indonesia (1.6 MYA?)
> |> 945.8 to China (about .6-1 MYA?) 1028.75, to Indonesia (abt .13 MYA?) at
> |> 1148.5. These values are CC's or ml's, and I 've had the honor of doing
> |> the endocranial casts from Indonesia and Solo, and feel confident about
> |> the values.

> The indonesian solo skulls were only 130,000 years old? That would
> provide significant overlap with archaic h. sapiens in africa.
I don't know the dates exactly, but roughly that order of time, possibly a
little later.

> |> The earliest erectus is possibly Lantian, not calculated in the above,
> |> although the KNM-ER 3733 (848) and KNM-ER 3883 ( 804) H. erectus (or
> |> ergaster if you prefer) are well above 800, particularly if OH 9 (1067)
> |> and KNM-WT 15000 (900) are combined as erectus: mean = 904.75ml. This is a
> |> fair amount greater than the 700 mentioned above.
> Yes; I'm not sure where I got that number.
> Any idea about pre-h. erectus cranial capacity? How big was an h.
> habilus brain?

The habilines are a problem, as it is unclear what they include. Is 1470
the same taxon as OH62, or OH7, how big was 1590, etc, etc. 1470=752ml
OH7 = ca 680ml
OH24 =590ml
OH13 650 ml
KNM-ER 3732 =est. 650 ml
What are KNM-ER 1813? =510 ml
and KNM-ER 1805, = 582ml
If the same taxon, average =630.57
If 1470 excluded as H. rudolphensis, Average=610.33ml
KNM-ER 1590 is rather massive, the parts fit over the 1470 cranium.
OH 62 has very few cranial fragments but seems most probably smallish to
me and I would doubt it was bigger than 600ml.
I would say, that perhaps 625 would to 680 would be a reasonable span for
H. habilis (whatever it is).
> Over the long run, it seems like a safe assumption; archaic h. sap
> populations of 150,000 b.p. with cranial capacities averaging 1200 cc
> were probably less intelligent than modern humans.

OK, but remember that the total evolutionary trajectory in hominid brain
brain size from early Australopithecus to Homo sapiens was about 1000 ml,
i.e., from about 450 to 1450ml. That is just about the same as the range
of normal variation in modern H. sapien's brain size, i.e., from about 900
to 2000, with very little demonstrable evidence for differences in
"intelligence" (except perhaps as measured by IQ scores, which I really
don't know what these tests measurethat might have been of survival value
during the Pleistocene). The next question: should the relationship be

> I have also read that modern east asian populations have the highest
> cranial capacity/body mass ratio among current humans, and they also
> have the highest IQ's. The possibility of a causal link can not be
> ruled out.

I agree the possible causal link cannot be ruled out entirely, but other
interpretations of the high Asian IQ exist which suggest cultural
mechanisms rather than brain size might be operative, manifested as a
genuine respect for education (not genetically linked as of yet...). How
can one test these two possible hypotheses and refute one of them, and
possibly others?

Ralph Holloway